1. Technical Field
The present invention relates to a baking oven, particularly for bread or confectionery. Such a baking oven is ideal for use both in bakeries which produce bread or confectionery (either on a small-scale or at industrial level) and in canteens and restaurants, where the use of frozen bread or confectionery which require on-site baking is becoming increasingly frequent.
2. Prior Art
As is known, in the type of oven described, the heat source may be a burner or electric heating elements, and the ovens may be separated into two categories: having fixed or rotary cooking surfaces.
In the latter type of oven, according to the prior art, heat is transferred into the oven and yielded to the product exclusively by means of hot air convection.
As a result, rotary ovens of the known type are unsuitable for baking delicate products, which may be damaged by the hot air flow, nor are they suitable for baking bread or those products which require a strong supply of heat at the base, that is to say, at the area in which they rest against the cooking surfaces.
As regards ovens with fixed cooking surfaces, these may use as a heat source either the forced circulation of hot air, or heat exchangers (e.g.: of the fire tube type), or electric heating elements.
In accordance with the prior art, ovens with fixed cooking surfaces, which use both cooking surface heating and forced air circulation, may substantially be divided into three types. The first type has heated cooking surfaces which separate various independent chambers, each chamber having an air flow, which does not supply heat, produced by a fan. Each independent chamber has its own access door.
This first type of oven with fixed cooking surfaces has, as is known, several disadvantages: since the chambers are independent, the number of cooking surfaces is limited; operating costs are relatively high because each chamber requires its own heating unit, and construction costs are equally high given the number of compartments and doors necessary; moreover, the overall dimensions of the oven are quite considerable.
A second type of oven has heated cooking surfaces positioned in a single chamber, with access door, an air flow which does not supply heat, produced by a fan envisaged within the chamber. A trolley with a number of shelves corresponding to the number of fixed cooking surfaces is also envisaged. The product is loaded onto the trolley, which is then placed in the oven's baking chambers, where the trolley shelves lie above the fixed cooking surfaces.
This second type of oven allows the economic disadvantage of the first type of oven mentioned to be resolved at least in part, although its own disadvantage lies in the fact that the heat yield from fixed cooking surface to product is not optimum due to the presence of the trolley shelf between them.
A third type of oven has a set of fixed cooking surfaces which are not heated. In this type of oven the product is heated by a forced convection hot air flow. The oven has a single door (which allows the insertion of a trolley ready-loaded with the product to be baked) which is, in turn, divided into a series of smaller doors, equivalent in number to the cooking surfaces.
This type of oven has the following main disadvantages: the absence of heated cooking surfaces does not permit the baking of those products which require a strong source of heat at the base, and the heat derived exclusively from the forced convection hot air flow does not allow the baking of delicate products, which may be damaged by the air.
The three types of oven mentioned above have not only the disadvantages described, but also significant functional disadvantages and limitations common to all three.
Firstly, such types of known ovens each have a single heat source (e.g.: a burner or electric heating elements, as in the first two cases described, or the forced convection of hot air, as in the third case), with a single temperature control system. With regard to this, it should be noticed that many types of product require a clearly defined ratio between the temperature of the cooking surface and the temperature of the air above (indicated here by the letter "R"). Variation of the said ratio R is impossible in the three types of oven described above, representing a significant functional limitation.
At present, the ratio R may be varied only in electric ovens with independent chambers, in which the temperature of the cooking surface and the temperature of the air at the top or the chambers can be regulated from the outside.
However, even electric ovens have several disadvantages which limit their use: they require a substantial current operating and construction costs are high variations in temperature are slow (therefore, these ovens cannot be used for products which require relatively sudden temperature variations during baking).
It may, therefore, be said that in all conventional ovens, with either fixed or rotary cooking surfaces, rapid variations in the baking temperature (useful for certain products) are impossible, as regards both the cooking surfaces and the air, if the oven is to be kept in optimum condition for the subsequent baking of other products. In reality, the temperature could be varied by adjusting the oven's heat source. However, this would necessitate an excessive amount of time to return the temperature to the operating level. Moreover, the duration of a cycle envisaging temperature variations would be very long using the known types of oven.